Fossil Fuckery

Question 1

Direct Preservation: Unaltered Remains

Answer 1

Preserved without any or very little change from original state, occurs in 3 ways: unaltered, desiccation, embedding

Question 2

Unaltered

Answer 2

hard parts (bones, teeth, shells) remain unchanged because they are resilliant

Question 3

Desiccation

Answer 3

Freezing or mummifcation

Question 4

Embedding

Answer 4

in wax or amber (desiccation also occurs in this mode)

Question 5

Direction Preservation: Altered Remains

Answer 5

• Most fossils are altered in some way. Changes may be chemical, physical, or both. Single fossil may have more than 1 or these forms:
  1. Recrystallization
  2. Replacement
  3. Premineralization
  4. Petrification
  5. Carbonization

Question 6

Recrystallization

Answer 6

Minerals of fossils change to a more stable form without change in composition. Involves increase in crystal size. In shells, makes them appear dull

Question 7

Replacement

Answer 7

Minerals of a fossil are replaced by new minerals with different compositions. Usually replaced by silica or pyrite.

Question 8

Permineralization

Answer 8

Pores (in bones usually) or empty body chambers are filled with a mineral, in wood as well

Question 9

Petrification

Answer 9

Organic tissue of a fossil is replaced with new mineral

Question 10

Carbonization

Answer 10

Volatiles (i.e water) are removed through heat and compaction leaving a thin carbon film

Question 11

Indirect preservation: Impressions

Answer 11

Physical remains of buried organism dissolve, but the shape is still preserved in the fossil record

Question 12

Molds

Answer 12

impression of remains like stamps of organisms = external mold. If interior of organism is filled with sediment/sedimentary minerals and shell dissolves away = internal mold

Question 13

Casts

Answer 13

Exact replicas of remains. If an external mold later fills with sediment/mineral an exact replica/cast is made

Question 14

Molds are negative

Answer 14

Inverse of the original shape

Question 15

Casts are positive

Answer 15

Same as the original shape

Question 16

Colonial Organisms

Answer 16

individuals living together in a single mass of interlocking, individual skeletons, recognized by presence of multiple openings which represent many individual homes

Question 17

Solitary organisms

Answer 17

not structurally bound to any other organism

Question 18

Steps in identifying fossil

Answer 18

1. Colonial/solitary

2. Describe overall shape of fossil

Question 19

Trace Fossils

Answer 19

• Objects or evidence of life activities fossilized in or on sediment layers
• Occur in marine and continental sedimentary rocks

Question 20

Types of Trace Fossils

Answer 20

1. Burrows and Borings
2. Resting Traces
3. Trackways, Trails and Footprints
4. Coprolites and Gastroliths

Question 21

Burrows and Borings

Answer 21

burrows in soft sediment or bore holes in solid rock/wood/shells, often tubular and horizontal for deposit feeding or dwelling

Question 22

Resting traces

Answer 22

When an animal stops moving for a short while, producing a shallow impression or mold on the sediment surface, may record their shape or morphology

Question 23

Trackways, Trails and Footprints

Answer 23

Evidence of animals travelling across soft sediment surfaces, preserved as molds on top of beds or casts on bottoms of overlying beds. Formed by organisms that are surface feeding or grazing.

Question 24

Coprolites

Answer 24

fossil excrement

Question 25

Gastroliths

Answer 25

Only identifiable if found in the gut area of a skeleton, rounded stomach stones used for grinding down food after its swallowed

Question 26

Incomplete Fossil Record

Answer 26

• Likelihood of an organism becoming a fossil is determined by its: structure, composition and environment it lived/died in
• Because sediment is constantly transported to bodies of water, deposition occurs relatively continuously in these settings
• More likely to have marine and freshwater organisms preserved than terrestrial = more complete fossil record of marine realm

Question 27

Fossils are generally better preserved in:

Answer 27

fine-grained sediment because fine grain sizes preserve small details

Question 28

Fossil/Biotic Succession

Answer 28

Relative dating principle that states that fossils in sedimentary rock units occur in particular vertical order, reflecting changes due to evolution

Question 29

Biostratigraphy/Biostratigraphic Correlation

Answer 29

Rock units in different locations can be correlated using the same principle and this method of showing correspondence of character and/or stratigraphic position between features or element in separate locations

Question 30

Index groups

Answer 30

few select groups used for regional and intercontinental correlations, individual fossils used = index fossils

Question 31

Index groups/fossils are abundant…

Answer 31

geographically widespread, and occur over restricted/short stratigraphic range = didn’t live for very long because evolved quickly or extinct

Question 32

Biozone

Answer 32

A restricted sequence of rock strata that records a discrete interval of Earth history, used for determining the age of rocks from fossils, identified by presence of specific fossil or group of fossils